The deal (I think) with the ergonomics of the FAL vs the M1A is that from the beginning, the FAL was designed as a full auto rifle, thus the pistol grip and the weight-forward feel of the rifle.
The M14 is an updated Garand, designed for the rifleman and thus the balance is further back and at least for me, just hangs better when fired from the shoulder. It was updated to full auto, but was never great in that role. However, the semi-auto civilian version returns it to its roots.
I think you'll be happy with both if you choose quality builds.